See my original build:
When I was troubleshooting, I found an app that was a virtual console port, that allowed me to see a comm port from the CLI. I used "minicom" and it was really helpful in troubleshooting my data connection to the TT4. You will have to install the package, which is available through the packages on the web interface.
If you still have problems, try the folling until you have better results:
Verify you have a ground between all of the devices (floating grounds will screw up data)
Try flipping the data lines.
Are you converting the RS232 into TTL 3.3v for the WRT54G router?